Apparatus for dispensing liquid crystal and method for controlling liquid crystal dropping amount

Abstract

A liquid crystal dispensing apparatus and a method of controlling a liquid crystal dropping amount are provided to drop liquid crystal onto a substrate corresponding to at least one unit panel area. In one aspect, the apparatus uses a liquid crystal dispensing unit to dispense liquid crystal. The liquid crystal dispensing unit includes a nozzle having a discharging hole through which the liquid crystal is dropped onto the substrate, a needle moveable between a down position in which the needle blocks the discharging hole and an up position in which the needle is separated from the discharging hole, a spring member to bias the needle toward the down position, and a solenoid coil to provide a magnetic force to move the needle to the up position. The dropping amount liquid crystal dispensing unit may be electrically controlled by controlling the solenoid coil or by controlling a gas pressure used to drive the liquid crystal through the discharging hole. Variations and errors in the dropping amount may also be compensated by an automated compensation of the electric power to the solenoid and/or the gas pressure.

What is claimed is:  
     
       1. A liquid crystal dispensing apparatus for dropping liquid crystal onto a substrate corresponding to at least one unit panel area, the apparatus comprising: 
       a liquid crystal dispensing unit to dispense liquid crystal, the liquid crystal dispensing unit including:  
       a nozzle having a discharging hole through which the liquid crystal is dropped onto the substrate,  
       a needle moveable between a down position in which the needle blocks the discharging hole and an up position in which the needle is separated from the discharging hole,  
       a spring member to bias the needle toward the down position, and  
       a solenoid coil to provide a magnetic force to move the needle to the up position;  
       an electric power supply unit to provide electric power to the solenoid coil to move the needle to the up position;  
       a gas supply unit to provide a gas pressure to the liquid crystal dispensing unit to drive the liquid crystal through the discharging hole when the needle is in the up position; and  
       a control unit to calculate a dropping amount of the liquid crystal to be dropped on the substrate and to control the electric power supply unit and the gas supply unit such that the calculated dropping amount of the liquid crystal is dispensed onto the substrate.  
     
     
       2. The apparatus according to  claim 1 , wherein the control unit includes: 
       an input unit through which data is input;  
       a dropping amount calculation unit to calculate the dropping amount of the liquid crystal and a dropping position of the liquid crystal onto the substrate according to the input data;  
       at least one of an electric power control unit control the electric power provided by the electric power supply unit to the solenoid coil according to the liquid crystal dropping amount calculated by the dropping amount calculation unit, and a flow control unit to control the gas pressure according to the liquid crystal dropping amount calculated by the dropping amount calculation unit; and  
       a substrate driving unit to drive one of the substrate and the liquid crystal dispensing unit with respect to the other so that the nozzle is positioned above the dropping position calculated by the dropping amount calculation unit.  
     
     
       3. The apparatus according to  claim 2 , wherein the input data includes at least an area of the liquid crystal panel unit, a cell gap of the liquid crystal unit panel, and characteristic information of the liquid crystal. 
     
     
       4. The apparatus according to  claim 2 , wherein the control unit further includes an output unit to display the input data, the calculated dropping amount of the liquid crystal, and a dropping status of the liquid crystal. 
     
     
       5. The apparatus according to  claim 2 , wherein the dropping amount calculation unit includes: 
       a total dropping amount calculation unit to calculate a total amount of the liquid crystal to be dropped onto the substrate according to the input data;  
       a dropping position calculation unit to calculate a dropping position of the liquid crystal according to the total amount of liquid crystal to be dropped calculated by the total dropping amount calculation unit;  
       a dropping number calculation unit to calculate a number of drops of the liquid crystal according to the total dropping amount calculated by total dropping amount calculation unit; and  
       a single dropping amount calculation unit to calculate a single drop amount of the liquid crystal according to the total dropping amount calculated by the total dropping amount calculation unit.  
     
     
       6. The apparatus according to  claim 1 , further comprising a compensating unit to compensate the dropping amount of the liquid crystal when a measured dropping amount of the liquid crystal being dropped is different from the calculated dropping amount of the main control unit. 
     
     
       7. The apparatus according to  claim 6 , wherein the compensating unit includes: 
       a dropping amount measuring unit to measure the measured dropping amount of the liquid crystal; and  
       a compensating amount calculation unit to compare the measured dropping amount and the calculated dropping amount, to calculate a compensating amount, and to drive the at least one of the electric power control unit and the flow control unit.  
     
     
       8. The apparatus according to  claim 7 , wherein the compensating amount calculation unit includes: 
       a dropping amount setting unit in which the dropping amount calculated in the main control unit is set;  
       a comparing unit to compare the dropping amount set in the dropping amount setting unit with the measured dropping amount and to calculate a difference value; and  
       a compensation calculation unit to calculate an error value of dispensing characteristic in order to compensate for the difference value calculated by the comparing unit.  
     
     
       9. The apparatus according to  claim 8 , wherein the compensation calculation unit includes at least one of: 
       a pressure error calculation unit to calculate an error value of the gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the difference value calculated in the comparing unit, to calculate the flow amount of the gas corresponding to the error value of the gas pressure, and to output the flow amount such that the gas pressure is compensated; and  
       an electric power error calculation unit to calculate an error value of the electric power amount applied to the solenoid coil based on the difference value calculated in the comparing unit and to output the error value of the electric power amount such that the electric power provided to the solenoid coil is compensated.  
     
     
       10. A method of dispensing a liquid crystal onto a substrate having at least one liquid crystal unit panel area from a liquid crystal dispenser using a gas pressure to dispense liquid crystal therefrom, the liquid crystal dispenser including a nozzle having a discharging opening from which the liquid crystal is dropped, a needle moveable between a down position to block the discharging opening and an up position to open the discharging opening, a spring to bias the needle toward the down position, and a solenoid coil to provide a magnetic force to open the discharging hole, the method comprising the steps of: 
       inputting data;  
       calculating a total dropping amount of the liquid crystal to be dropped onto the substrate according to the input data;  
       calculating a dropping position at which liquid crystal is to be dropped onto the substrate according to the calculated total dropping amount;  
       calculating a single dropping amount of the liquid crystal according to the total dropping amount;  
       calculating an amount of electric power to be supplied to the solenoid coil and a gas pressure to be applied onto the liquid crystal in the liquid crystal dispenser according to the calculated single dropping amount; and  
       applying the calculated amount of the electric power to the solenoid coil and supplying the calculated gas pressure to the liquid crystal dispenser.  
     
     
       11. The method according to  claim 10 , wherein the step of inputting data includes inputting an area of the liquid crystal unit panel, a cell gap of the liquid crystal panel, and characteristic information of the liquid crystal. 
     
     
       12. The method according to  claim 10 , further comprising a step of controlling a tension of the spring. 
     
     
       13. The method according to  claim 12 , wherein the step of controlling the tension of the spring includes an operator setting the tension at an initial stage of the liquid crystal dropping. 
     
     
       14. The method according to  claim 13 , further comprising the step of displaying the input data, the calculated dropping amount of the liquid crystal, and a dropping status of the liquid crystal. 
     
     
       15. The method according to  claim 10 , wherein the step of compensating the dropping amount of the liquid crystal includes the steps of: 
       measuring the measured amount the liquid crystal dropped; and  
       calculating a compensating amount by comparing the measured dropping amount with the calculated single dropping amount; and  
       controlling at least one of the electric power applied to the solenoid coil and the gas pressure according to the calculated compensating amount.  
     
     
       16. The method according to  claim 15 , wherein the gas pressure corresponding to a single dropping amount is fixed at an initial stage of the liquid crystal dropping. 
     
     
       17. The method according to  claim 15 , further comprising a step of compensating the dropping amount of the liquid crystal if a measured amount of the liquid crystal dropped on the substrate is different from the calculated single dropping amount. 
     
     
       18. The method according to  claim 10 , wherein the amount of electric power corresponding to a single dropping amount of the liquid crystal is fixed at an initial stage of the liquid crystal dropping. 
     
     
       19. A liquid crystal dispensing apparatus for dropping liquid crystal onto a substrate, comprising: 
       a liquid crystal dispensing unit to dispense liquid crystal;  
       a measuring system to measure an amount of liquid crystal dispensed from the dispensing unit; and  
       a controller to receive the measured amount of liquid crystal from the measuring system, the controller comparing the measured amount of liquid crystal with a target amount of liquid crystal to be dispensed and electrically adjusting at least one dispensing characteristic of the liquid crystal dispensing unit if the measured amount is different than the target amount.  
     
     
       20. The apparatus according to  claim 19 , wherein the liquid crystal dispensing unit includes a nozzle having a discharging opening from which the liquid crystal is dropped, a needle moveable between a down position to block the discharging opening and an up position to open the discharging opening, a spring to bias the needle toward the down position, and a solenoid coil to provide a magnetic force to open the discharging hole. 
     
     
       21. The apparatus according to  claim 20 , wherein a gas pressure is used to drive the liquid crystal through the discharging opening when the needle is in the up position. 
     
     
       22. The apparatus according to  claim 21 , wherein the controller controls at least one of the gas pressure and the solenoid coil to adjust the at least one dispensing characteristic of the liquid crystal dispensing unit. 
     
     
       23. A liquid crystal dispensing apparatus for dropping liquid crystal onto a substrate corresponding to at least one unit panel area, the apparatus comprising: 
       a liquid crystal dispensing unit to dispense liquid crystal, the liquid crystal dispensing unit including:  
       a nozzle having a discharging hole through which the liquid crystal is dropped onto the substrate,  
       a needle moveable between a down position in which the needle blocks the discharging hole and an up position in which the needle is separated from the discharging hole,  
       a spring member to bias the needle toward the down position, and  
       a solenoid coil to provide a magnetic force to move the needle to the up position;  
       a dropping amount measuring unit to measure a dropping amount of liquid crystal dropped;  
       a compensating amount calculation unit to compare the measured dropping amount with a target dropping amount to calculate a compensating value; and  
       a compensating control unit to control at least one of the electric power applied to the solenoid coil and the gas pressure according to the compensating value.  
     
     
       24. The apparatus according to  claim 23 , wherein the compensating control unit includes at least one of: 
       an electric power control unit to control the electric power applied to the solenoid coil according to the compensating amount calculated in the compensating amount calculation unit; and  
       a flow control unit to control a gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the compensating amount calculated in the compensating amount calculation unit.  
     
     
       25. The apparatus according to  claim 23 , wherein the dropping amount measuring unit includes a gravimeter adjacent to the substrate. 
     
     
       26. The apparatus according to  claim 23 , wherein the dropping amount measuring unit measures the dropping amount by measuring a total dropping amounts of set number of drops. 
     
     
       27. The apparatus according to  claim 23 , wherein the compensating amount calculation unit includes: 
       a dropping amount setting unit in which the target dropping amount is set;  
       a comparing unit to compare the dropping amount with the measured dropping amount and to calculate a difference value; and  
       an electric power error calculation unit to calculate an error value of an electric power amount applied to the solenoid coil according to the difference value calculated in the comparing unit and to output the error value to control the electric power amount applied to the solenoid coil.  
     
     
       28. The apparatus according to  claim 23 , wherein the compensating amount calculation unit includes: 
       a dropping amount setting unit in which the target dropping amount is set;  
       a comparing unit to compare the dropping amount with the measured dropping amount and to calculate a difference value; and  
       a pressure error calculation unit to calculate an error value of the gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the difference value calculated in the comparing unit and to output the error value to control the gas pressure.  
     
     
       29. The apparatus according to  claim 23 , wherein the compensating amount calculation unit comprises: 
       a dropping amount setting unit in which the target dropping amount is set;  
       a comparing unit to compare the dropping amount with the measured dropping amount and to calculate a difference value;  
       a pressure error calculation unit to calculate an error value of the gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the difference value calculated in the comparing unit and to output the error value of the gas pressure to control the gas pressure; and  
       an electric power error calculation unit to calculate an error value of an electric power amount applied to the solenoid coil according to the difference value calculated in the comparing unit and to output the error value of the electric power amount to control the electric power amount applied to the solenoid coil.  
     
     
       30. A method of dispensing liquid crystal onto a substrate corresponding to at least one unit panel area, the method comprising the steps of: 
       filling a liquid crystal dispensing unit with liquid crystal;  
       dispensing a first quantity of liquid crystal onto the substrate;  
       conducting an automated compensation of at least one dispensing characteristic of the liquid crystal dispensing unit; and  
       dispensing a second quantity of the liquid crystal onto the substrate, the second quantity being determined according to the automated compensation.  
     
     
       31. The method according to  claim 30 , wherein the step of conducting the automated compensation includes the steps of 
       dispensing a test quantity of liquid crystal to a measuring system substantially adjacent to the substrate;  
       measuring the amount of liquid crystal dispensed in the test quantity;  
       comparing the measured amount with a target amount; and  
       automatically adjusting the at least one dispensing characteristic of the liquid crystal dispensing unit.  
     
     
       32. The method according to  claim 31 , wherein the liquid crystal dispensing unit includes at least one of an electrically controlled valve structure to control the dispensing of the liquid crystal and an electrically controlled gas supply to apply a gas pressure in order to drive the dispensing of the liquid crystal when the electrically controlled valve structure is open, and wherein the step of automatically adjusting the dispensing characteristics includes the step of electrically adjusting at least one of the electrically controlled valve structure and electrically controlled the gas supply. 
     
     
       33. The method according to  claim 32 , wherein the electrically controlled valve structure includes a nozzle having discharging hole and a needle moveable between a first position to close the discharging hole and a second position to open the discharging hole. 
     
     
       34. A method of dispensing a liquid crystal from a liquid crystal dispenser using a gas pressure to dispense liquid crystal therefrom, the liquid crystal dispenser including a nozzle having a discharging opening from which the liquid crystal is dropped, a needle moveable between a down position to block the discharging opening and an up position to open the discharging opening, a spring to bias the needle toward the down position, and a solenoid coil to provide a magnetic force to open the discharging hole, the method comprising the steps of: 
       setting a dropping amount of the liquid crystal to be dropped;  
       measuring an amount of liquid crystal dropped;  
       calculating a compensating amount by comparing the set dropping amount with the measured dropping amount; and  
       controlling at least one of an electric power applied to the solenoid coil and the gas pressure applied to the liquid crystal according to the calculated compensating amount.  
     
     
       35. The method according to  claim 34 , wherein the dropping amount of the liquid crystal is calculated according to an area of a liquid crystal unit panel, a cell gap of the liquid crystal unit panel, and characteristic information of the liquid crystal. 
     
     
       36. The method according to  claim 34 , wherein the step of measuring the amount of liquid crystal dropped includes the step of measuring a weight of the liquid crystal dropped. 
     
     
       37. The method according to  claim 34 , wherein the step of calculating the compensating amount includes the steps of: 
       calculating a difference value by comparing the set dropping amount with the measured dropping amount;  
       calculating an error value of the gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the calculated difference value in the dropping amount; and  
       calculating a gas flow amount corresponding the calculated error value.  
     
     
       38. The method according to  claim 34 , wherein the step of calculating the compensating amount includes the steps of: 
       calculating a difference value by comparing the set dropping amount with the measured dropping amount;  
       calculating an error amount of the electric power applied to the solenoid coil according to the difference value; and  
       calculating an electric power corresponding to the calculated error value.  
     
     
       39. The method according to  claim 34 , wherein the step of calculating the compensating amount includes the steps of: 
       calculating a difference value by comparing the set dropping amount with the measured dropping amount;  
       calculating an error value of the gas pressure applied to the liquid crystal in the liquid crystal dispensing unit according to the calculated difference value in the dropping amount to determine a gas flow amount corresponding the calculated error value of the gas pressure; and  
       calculating an error amount of the electric power applied to the solenoid coil according to the difference value to determine an electric power corresponding to the calculated error value.  
     
     
       40. The method according to  claim 34 , further comprising the step of controlling a tensile force of the spring in accordance with the calculated compensating amount.